Many machines, particularly internal combustion engines, include a pressurized lubrication system essential to continued machine operation. Lubrication fluid circulates through the machine to maintain the machine cool and avoid damage by reducing friction as it circulates past points of metal-to-metal contact such as bearing surfaces. The lubrication system must maintain a given volume of lubrication fluid, e.g., oil, and must maintain operating temperatures within acceptable parameters. Lubricating fluid, however, degrades over time and changes its viscosity and ability to protect against expensive machine damage. A lubrication system breach, e.g., oil leak, reduces the available lubrication fluid and potentially exposes the machine to damage. A plug in a lubrication system prevents oil flow and also potentially exposes the machine to damage. As machine temperature varies during operation so does lubrication fluid viscosity and its ability to protect.
Many machines include an instrument panel providing indication of operating conditions. For example, an oil pressure gauge and a temperature gauge provide to the operator an indication of the oil pressure and engine temperature. The operator observes such gauges during operation to verify acceptable lubrication system parameters. The operator, if necessary, shuts down the machine when instrument gauges indicate operation outside acceptable parameters, e.g., a lubrication system failure due to loss of lubricant, excess temperature, or significant lubricant degradation.
Unfortunately, oil pressure varies significantly while remaining within normal operation, e.g., as a function of but not limited to variation in engine temperature or engine revolutions per minute (RPM). Engine temperature can vary significantly while remaining within normal or acceptable parameters. Because the lubricating oil pressure and temperature vary in complex fashion, it is not generally possible to identify by operator-interpretation of these gauge readings a need for engine shutdown. In other words an operator cannot always detect potentially damaging conditions within the engine by merely observing the oil pressure and temperature gauges. Oil and temperature gauoes can indicate gross excursions from acceptable parameters however, engine damage can occur when more subtle combinations of these engine operating conditions exist. Accordingly, an operator observing and interpreting oil and temperature gauges may not recognize such unacceptable engine operating conditions. By the time an operator realizes that the oil pressure and engine temperature have exceeded acceptable parameters, significant damage to the engine often has already occurred.
In addition to operator-interpretation of machine parameters by way of an instrument panel, some machines employ automatic shut down systems to prevent machine damage. One machine parameter of particular concern is oil pressure. Because oil pressure varies significantly as a function of oil flow rate through the engine, the physical size of passages of the flow path through the engine, and the temperature and viscosity of the oil flowing through the flow path, automated engine shut down devices remain generally incapable of accurately detecting all potentially enlgine-damaging operating conditions. In other words, oil pressure varies widely during normal enginie operation and existing automated shut down devices must necessarily allow broad variation without automated engine shut down. For extreme variations in oil pressure, an engine shut down can occur with these existing shutdown devices. Unfortunately, potentially engine-daiiatling conditions do arise with some degree of oil pressure and a device reacting to only a relatively low oil pressure fails to reliably avoid engine damage. Thus, automated engine shut down devices have not reliably detected all potentially engine-damaging lubrication conditions.
The subject matter of the present invention provides an automated monitor for an engine lubrication system allowing for normal variation in oil pressure and temperature, yet providing an alarm or shut down signal when engine conditions fall outside acceptable operating parameters.